Retroviruses are small, single stranded RNA viruses. Numerous species are susceptible to retroviral infection. While retroviral infection does not necessarily interfere with the normal life cycle of an infected cell or organism, retroviruses can be oncogenic, and retroviruses are responsible for diseases of the immune system in higher animals, including acquired immune deficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV).
Progress has been made in the development of drugs for HIV therapy. Among other things, U.S. Pat. No. 6,172,110 to Lee et al. describes acylated betulins for the treatment of HIV, U.S. Pat. No. 5,679,828 to Lee et al. describes betulinic acid derivatives for the treatment of HIV, and U.S. Pat. No. 5,468,888 to Bouboutou et al. describes lupane derivatives for the treatment of HIV. Specific examples of compounds that have been described for the treatment of HIV are the following:

Nevertheless, many drugs exhibit severe toxicities, have side effects, require complicated dosing schedules, or—most problematically—can lead to the development of drug resistance thereto in the subject being treated. These problems are further exacerbated in countries where high cost multiple drug therapy is not readily affordable to the general population. Hence there remains a need for new compounds useful for treating HIV, including for the treatment of strains of HIV that are resistant to treatment with other known compounds. There particularly remains a need for new compounds that have multiple modes of activity in treating HIV-1 infection.